Maintenance and repair work must be carried out in chemical and petrochemical plants at regular intervals. Persons who perform the work on site are subject to acute danger due to escaping gases and vapors in case of leaks or an accident. In addition to other protective gear, workers therefore carry, as a rule, gas-measuring devices with them, which generate an acoustic alarm if increased gas concentrations develop. Additional safety is offered by stationary or temporarily mounted, semi-stationary gas-measuring devices. The affected parts of the plant are evacuated in case of alarms. It may, however, happen in case of major accidents that evacuation is not possible in time and workers become unable to move due to poisoning or other effects.
Rescue workers now face the task of gaining an overview of the situation as quickly as possible and possibly to find persons who may have had an accident. However, since industrial plants are often highly complex and have a confusing arrangement, this may take a rather long time and accident victims may only be reached with a considerable delay.